阅读说明：本技术 一种减阻剂、其制备方法及在高钙镁离子环境中的应用 (Drag reducer, preparation method thereof and application thereof in high-calcium magnesium ion environment ) 是由 宋志峰 赵海洋 李新勇 秦飞 耿宇迪 张�雄 张俊江 罗攀登 王洋 刘志远 陈定 于 2019-10-21 设计创作，主要内容包括：本发明提供了一种减阻剂、其制备方法及在高钙镁离子环境中的应用。所述减阻剂具有如式I的结构式：式I,其中,x、y、z和w为整数；R-1为H、甲基、乙基、正丙基和异丙基中的一种；M为Na或K；R-2、R-3独立地为H、甲基、乙基、正丙基和异丙基中的一种；n-1为整数,且5≥n-1≥1；R-4为H、甲基、乙基、正丙基和异丙基中的一种；R-5为甲基、乙基、丙基、丁基、戊基、己基、庚基、辛基、壬基、癸基、C-(11)至C-(16)的烷基、聚氧乙烯醚中的一种；n-2为整数,且3≥n-2≥1；R-6为环己烷基、甲基环己烷基、苯基、甲基苯基、对甲基苯基中的一种。(The invention provides a drag reducer, a preparation method thereof and application in a high-calcium magnesium ion environment. The drag reducer has a structural formula as shown in formula I: formula I, wherein x, y, z and w are integers; r 1 Is one of H, methyl, ethyl, n-propyl and isopropyl; m is Na or K; r 2 、R 3 Independently is one of H, methyl, ethyl, n-propyl and isopropyl; n is 1 Is an integer of 5 or moren 1 ≥1；R 4 Is one of H, methyl, ethyl, n-propyl and isopropyl; r 5 Is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, C 11 To C 16 One of alkyl and polyoxyethylene ether of (1); n is 2 Is an integer of 3. gtoreq.n 2 ≥1；R 6 Is one of cyclohexane, methyl cyclohexane, phenyl, methyl phenyl and p-methyl phenyl.)

1. A drag reducer having a structure as shown in formula I,

wherein x, y, z and w are integers;

R₁is one of H, methyl, ethyl, n-propyl and isopropyl;

m is Na or K;

R₂、R₃independently is one of H, methyl, ethyl, n-propyl and isopropyl;

n₁is an integer of 5. gtoreq.n₁≥1；

R₄Is one of H, methyl, ethyl, n-propyl and isopropyl;

R₅is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, C₁₁To C₁₆One of alkyl and polyoxyethylene ether of (1);

n₂is an integer of 3. gtoreq.n₂≥1；

R₆Is one of cyclohexane, methyl cyclohexane, phenyl, methyl phenyl and p-methyl phenyl;

preferably, the drag reducer has a number average molecular weight of 800 to 920 ten thousand.

2. A process for preparing the drag reducer of claim 1, comprising the steps of:

step 1), dissolving A, B, C and D monomers in water, and adjusting the pH value to obtain a water phase mixed solution;

step 2), dissolving an emulsifier in the oil phase to obtain an oil phase mixed solvent;

step 3), mixing the water-phase mixed solution with the oil-phase mixed solvent to obtain an emulsion;

step 4), introducing nitrogen into the emulsion to remove oxygen, adding an initiator under a stirring state to obtain a reaction system, and reacting the reaction system to obtain a drag reducer;

wherein the structural formula of the monomer A is as follows:

wherein R is₁Is H, methyl, ethyl, n-propyl and isopropylOne of (1);

the structural formula of the monomer B is as follows:

wherein M is Na or K;

the structural formula of monomer C is as follows:

wherein R is₂、R₃Independently is one of H, methyl, ethyl, n-propyl and isopropyl; n is₁Is an integer of 5. gtoreq.n₁≥1；

The structural formula of monomer D is as follows:

wherein R is₄Is one of H, methyl, ethyl, n-propyl and isopropyl; r₅Is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, C₁₁To C₁₆One of alkyl and polyoxyethylene ether of (1); n is₂Is an integer of 3. gtoreq.n₂≥1，R₆Is one of cyclohexane, methyl cyclohexane, phenyl, methyl phenyl and p-methyl phenyl;

preferably, the drag reducer has a number average molecular weight of 800 to 920 ten thousand.

3. The method according to claim 2, wherein in step 1), the amount of the monomer A, the monomer B, the monomer C and the monomer D is 15 to 30%, 3 to 9%, 2 to 6% and 0.01 to 1% in sequence, based on 100% by mass of water; and/or

In the step 2), the mass of the oil phase mixed solvent is taken as 100%, the mass of the oil phase is 85-90%, and the mass of the emulsifier is 10-15%;

preferably, the mass of the emulsifier is 4% to 9% by mass based on 100% by mass of the emulsion.

4. The method of claim 2 or 3, wherein the oil phase is a white oil; and/or

The emulsifier is at least one of Span80, Tween20, OP-10 and Tween 60; and/or

The initiator is at least one of a composition formed by sodium bisulfite and ammonium persulfate, azobisisobutyrimidazoline hydrochloride and azobisisobutyronitrile.

5. The method according to any one of claims 2 to 4, wherein in step 1), the pH value after pH adjustment is 6 to 7, and/or

In step 2), the HLB value of the oil-phase mixed solvent is 5 to 6.

6. The method according to any one of claims 2 to 5, wherein in step 3), the mass ratio of the water-phase mixed solution to the oil-phase mixed solvent is 3:2 to 2: 3.

7. The method according to any one of claims 2 to 6, characterized in that, in step 3), the aqueous phase mixture is added dropwise to the oil phase mixture solvent to be mixed by sufficient stirring.

8. The process according to any one of claims 2 to 7, characterized in that in step 4) nitrogen is passed for a period of 30 to 60 minutes.

9. The method according to any one of claims 2 to 8, characterized in that, in step 4), the initiator is added at 30 to 60 ℃ and the reaction system is allowed to react for 2 to 4 hours;

the amount of the initiator is preferably 0.01% to 0.1% based on 100% by mass of the total mass of the drag reducer.

10. Use of a drag reducer according to claim 1 or prepared according to the process of any one of claims 2 to 9 in a highly mineralized environment;

preferably, the drag reducer is applied in an environment of high mineralization and high calcium and magnesium ions.

Technical Field

The invention provides a drag reducer and a method for preparing the drag reducer, and particularly relates to application of the drag reducer in a high-calcium magnesium ion environment.

Background

The prior art drag reducers have achieved some success with respect to salt tolerance issues, but these efforts have been primarily directed to monovalent salts. For high content of divalent calcium and magnesium ions (>1.0×10⁴mg/L) of the drag reducer in the liquid, the problems of solubility and drag reduction are still unsolved.

Therefore, there is a need to develop a drag reducer having high mineralization resistance and high calcium and magnesium ions.

Disclosure of Invention

One aspect of the present invention provides a drag reducer having a structure as shown in formula I,

wherein x, y, z and w are integers;

R₁is one of H, methyl, ethyl, n-propyl and isopropyl;

m is Na or K;

R₂、R₃independently is one of H, methyl, ethyl, n-propyl and isopropyl;

n₁is an integer of 5. gtoreq.n₁≥1；

R₄Is one of H, methyl, ethyl, n-propyl and isopropyl;

R₅is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, C₁₁To C₁₆One of alkyl and polyoxyethylene ether of (1);

n₂is an integer of 3. gtoreq.n₂≥1；

R₆Is one of cyclohexane, methyl cyclohexane, phenyl, methyl phenyl and p-methyl phenyl.

Wherein the values of x, y, z and w in formula I can be determined based on the number average molecular weight of the compound of formula I and the amount of each monomer used in the preparation process.

In one embodiment, the drag reducer has a number average molecular weight of 800 to 920 ten thousand.

The second aspect of the present invention provides a method for preparing a drag reducer according to the first aspect of the present invention, comprising the steps of:

step 1), dissolving A, B, C and D monomers in water, and adjusting the pH value to obtain a water phase mixed solution;

step 2), dissolving an emulsifier in the oil phase to obtain an oil phase mixed solvent;

step 3), mixing the water-phase mixed solution with the oil-phase mixed solvent to obtain an emulsion;

step 4), introducing nitrogen into the emulsion to remove oxygen, adding an initiator under a stirring state to obtain a reaction system, and reacting the reaction system to obtain a drag reducer;

wherein the structural formula of the monomer A is as follows:

wherein R is₁Is one of H, methyl, ethyl, n-propyl and isopropyl;

the structural formula of the monomer B is as follows:

wherein M is Na or K;

the structural formula of monomer C is as follows:

wherein R is₂、R₃Independently is one of H, methyl, ethyl, n-propyl and isopropyl; n is₁Is an integer, and 5>n₁≥1；

The structural formula of monomer D is as follows:

wherein R is₄Is one of H, methyl, ethyl, n-propyl and isopropyl; r₅Is methyl, ethyl, propyl, butyl, pentyl, hexyl,Heptyl, octyl, nonyl, decyl, C₁₁To C₁₆One of alkyl and polyoxyethylene ether of (1); n is₂Is an integer, and 3>n₂≥1，R₆Is one of cyclohexane, methyl cyclohexane, phenyl, methyl phenyl and p-methyl phenyl.

In one embodiment, the drag reducer has a number average molecular weight of 800 to 920 ten thousand.

In one embodiment, in step 1), the amount of the monomer a, the monomer B, the monomer C, and the monomer D is 15% to 30%, 3% to 9%, 2% to 6%, and 0.01% to 1% in this order, based on 100% by mass of water.

In one embodiment, in step 2), the mass of the oil phase is 85% to 90% and the mass of the emulsifier is 10% to 15% based on 100% by mass of the oil-phase mixed solvent.

In one embodiment, the emulsifier is present in an amount of 4% to 9% by mass based on 100% by mass of the emulsion.

In one embodiment, the oil phase is a white oil.

In one embodiment, the emulsifier is at least one of Span80, Tween20, OP-10, and Tween 60.

In one embodiment, the initiator is at least one of a composition formed by sodium bisulfite and ammonium persulfate, azobisisobutyrimidazoline hydrochloride, and azobisisobutyronitrile.

In a particular embodiment, in step 1), the pH value after pH adjustment is 6 to 7.

In one embodiment, in step 2), the HLB value after adjusting HLB is 5 to 6.

In one embodiment, in step 3), the mass ratio of the water-phase mixed solution to the oil-phase mixed solvent is 3:2 to 2: 3.

In one embodiment, in step 3), the aqueous phase mixed solution is (slowly) added dropwise to the oil phase mixed solvent to be mixed by sufficient stirring.

In one embodiment, in step 4), nitrogen is bubbled for a period of 30 to 60 minutes.

In one embodiment, in step 4), the initiator is added at 30 to 60 ℃ and the reaction system is allowed to react for 2 to 4 hours.

In one embodiment, the initiator is used in an amount of 0.01% to 0.1% based on 100% of the total mass of the drag reducer.

The third aspect of the invention provides the use of a drag reducer according to the first aspect of the invention or prepared according to the method of any of the second aspects of the invention in a hypersaline environment.

In one embodiment, the drag reducer is used in a highly mineralized and high calcium magnesium ion environment.

In the present invention, hypersalinity means a degree of mineralization of 20X 10⁴mg/L or more.

In the present invention, high calcium ion means that calcium ion is 10000mg/L or more.

In the present invention, high magnesium ion means magnesium ion of 2000mg/L or more.

The invention has the beneficial effects that:

the invention has simple production process, high production efficiency, low production cost and excellent salt-resistant effect, increases the practicability of the drag reducer, and simultaneously, the prepared drag reducer has quick solubility, good shear resistance, good fluidity and convenient use. The drag reduction rate of the 0.1 percent drag reducer clear water can reach 74.71 percent at most, and the high-strength shear is resisted. 0.15% drag reducer in highly mineralized (20X 10)⁴mg/L or more) and high calcium magnesium ion (10000mg/L Ca)²⁺Above +2000Mg/L Mg²⁺Above) the drag reduction rate was maintained at 71.82% at the highest under the saline conditions. The salt-tolerant drag reducer can effectively utilize a large amount of formation water and formation return drainage water, thereby reducing the field use cost, fully utilizing water resources and effectively protecting the environment.

Detailed Description

The present invention is further illustrated by the following examples, which are intended to be purely exemplary of the invention and are not to be construed as limiting the invention in any way.

Unless otherwise specified, the reagents used in the following examples are commercially available.

The structural formula of the monomer A is as follows:

wherein R is₁Is one of H, methyl, ethyl, n-propyl and isopropyl.

The structural formula of the monomer B is as follows:

wherein M is Na or K.

The structural formula of monomer C is as follows:

wherein R is₂、R₃Independently is one of H, methyl, ethyl, n-propyl and isopropyl; n is₁Is an integer of 5. gtoreq.n₁≥1。

The structural formula of monomer D is as follows:

wherein R is₄Is one of H, methyl, ethyl, n-propyl and isopropyl; r₅Is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, C₁₁To C₁₆One of alkyl and polyoxyethylene ether of (1); n is₂Is an integer of 3. gtoreq.n₂≥1，R₆Is one of cyclohexane, methyl cyclohexane, phenyl, methyl phenyl and p-methyl phenyl.

Example 1

In the monomer A, R₁Is H; in the monomer B, M is K; in the monomer C, R₂And R₃Are each methyl, n₁Is 1; in the monomer D, R₄Is H, R₅Is C₁₂Alkyl radical, n₂Is 2, R₆Is phenyl.

The process for preparing a drag reducing agent comprises the steps of:

firstly, dissolving each monomer in deionized water, and adjusting the pH value to 6.5 by using sodium hydroxide to obtain a water phase mixed solution. Wherein, the mass of the deionized water is taken as 100 percent, and the dosage of the monomer A, the monomer B, the monomer C and the monomer D is 15 percent, 3 percent, 2 percent and 0.01 percent in sequence.

And secondly, dissolving the emulsifier in the oil phase to obtain an oil phase mixed solvent, wherein the HLB value is 6. Wherein the oil phase is 85% of white oil, the emulsifier is Span80 and Tween20 with the total mass of 15%, and the mass ratio of Span80 to Tween20 is 4:1, wherein the oil phase is 100% of the oil phase mixed solvent.

And thirdly, slowly dripping the water-phase mixed solution prepared in the first step into the oil-phase mixed solvent prepared in the second step at the speed of 1 drop/second according to the mass ratio of 3:2, and fully stirring to obtain the emulsion. The total mass of the emulsion (approximately equal to the total mass of the drag reducer) is taken as 100%, and the content of the emulsifier is calculated to be 6%.

And fourthly, introducing nitrogen into the emulsion to remove oxygen for 30min, adding sodium bisulfite at 35 ℃ under the stirring condition of 600r/min, adding ammonium persulfate after 30mins, and stirring and reacting for 2 hours at 600r/min at the temperature to obtain the milky drag reducer. Wherein the total mass of the drag reducer is 100 percent, the dosage of the sodium bisulfite is 0.005 percent, and the dosage of the ammonium persulfate is 0.005 percent.

The number average molecular weight of the drag reducer prepared was 800 ten thousand as determined by gel permeation chromatography.

And (3) evaluating the resistance reduction effect: the drag reduction ratio was determined using the drag reducer for slickwater (emulsion type) specifications in DB 61/T1190-2018. Wherein, the drag reduction rate of the drag reducer with the mass content of 0.1 percent in clear water is determined; the drag reducer is determined at 20X 10⁴High salinity and high calcium and magnesium ion (10000mg/L Ca)²⁺+2000mg/L Mg²⁺) The drag reduction rate when the mass content of the brine is 0.15%. The results are shown in Table 1.

Example 2

In the monomer A, R₁Is H; in the monomer B, M is Na; in the monomer C, R₂And R₃Are each methyl, n₁Is 1; in the monomer D, R₄Is methyl, R₅Is octyl, n₂Is 2, R₆Is phenyl.

The process for preparing a drag reducing agent comprises the steps of:

firstly, dissolving each monomer in deionized water, and adjusting the pH value to 7 by using sodium hydroxide to obtain a water phase mixed solution. Wherein, the mass of the deionized water is taken as 100 percent, and the dosage of the monomer A, the monomer B, the monomer C and the monomer D is 20 percent, 6 percent, 4 percent and 0.5 percent in sequence.

And secondly, dissolving the emulsifier in the oil phase to obtain an oil phase mixed solvent, wherein the HLB value is 6. Wherein the oil phase is 85% of white oil, the emulsifier is OP-10 and Tween60 with the total mass of 15%, and the mass ratio of OP-10 to Tween60 is 6: 1.

And thirdly, slowly dripping the water-phase mixed solution prepared in the first step into the oil-phase mixed solvent prepared in the second step at the speed of 1 drop/second according to the mass ratio of 1:1, and fully stirring to obtain the emulsion. The total mass of the emulsion (approximatively, the total mass of the drag reducer) was taken as 100%, and the content of the emulsifier was calculated to be 7.5%.

And fourthly, introducing nitrogen into the emulsion to remove oxygen for 30min, adding sodium bisulfite at the temperature of 35 ℃ under the stirring condition of 800r/min, adding ammonium persulfate after 30mins, and stirring and reacting for 4 hours at the temperature of 800r/min to obtain the milky drag reducer. Wherein the total mass of the drag reducer is taken as 100 percent, the dosage of the sodium bisulfite is 0.05 percent, and the dosage of the ammonium persulfate is 0.05 percent.

The number average molecular weight of the drag reducer prepared was 900 ten thousand as determined by gel permeation chromatography.

The evaluation of the drag reduction effect was conducted in the same manner as in example 1, and the results are shown in Table 1.

Example 3

In the monomer A, R₁Is H; in the monomer B, M is K; in the monomer C, R₂And R₃Are each methyl, n₁Is 1; in the monomer D, R₄Is H, R₅Is hexyl, n₂Is 2, R₆Is phenyl.

The process for preparing a drag reducing agent comprises the steps of:

firstly, dissolving each monomer in deionized water, and adjusting the pH value to 6 by using sodium hydroxide to obtain a water phase mixed solution. Wherein the mass of the deionized water is taken as 100 percent, and the dosage of the monomer A, the monomer B, the monomer C and the monomer D is 30 percent, 9 percent, 6 percent and 1 percent in sequence.

And secondly, dissolving the emulsifier in the oil phase to obtain an oil phase mixed solvent, wherein the HLB value is 5. Wherein the oil phase is white oil accounting for 90 percent of the mass of the oil phase mixed solvent, and the emulsifier is Span80 and OP-10 accounting for 10 percent of the total mass, wherein the mass ratio of Span80 to OP-10 is 4: 1.

And thirdly, slowly dripping the water-phase mixed solution prepared in the first step into the oil-phase mixed solvent prepared in the second step at the speed of 1 drop/second according to the mass ratio of 2:3, and fully stirring to obtain the emulsion. The total mass of the emulsion (approximately equal to the total mass of the drag reducer) is taken as 100%, and the content of the emulsifier is calculated to be 6%.

And fourthly, introducing nitrogen into the emulsion to remove oxygen for 30min, adding an azo thermal dispersion initiator V044 (azobisisobutyrimidazoline hydrochloride (AIBI)) under the stirring conditions of 60 ℃ and 1000r/min, and stirring at 1000r/min for reaction for 2 hours at the temperature to obtain the emulsion drag reducer. Wherein the dosage of V044 is 0.01 percent based on the total mass of the drag reducer as 100 percent.

The number average molecular weight of the drag reducer copolymer produced was 850 ten thousand as determined by gel permeation chromatography.

The evaluation of the drag reduction effect was conducted in the same manner as in example 1, and the results are shown in Table 1.

Example 4

In the monomer A, R₁Is H; in the monomer B, M is Na; in the monomer C, R₂And R₃Are each methyl, n₁Is 1; in the monomer D, R₄Is methyl, R₅Is C₁₂Alkyl radical, n₂Is 1, R₆Is phenyl.

The process for preparing a drag reducing agent comprises the steps of:

firstly, dissolving each monomer in deionized water, and adjusting the pH value to 6 by using sodium hydroxide to obtain a water phase mixed solution. Wherein, the mass of the deionized water is taken as 100 percent, and the dosage of the monomer A, the monomer B, the monomer C and the monomer D is 20 percent, 6 percent, 4 percent and 0.1 percent in sequence.

And secondly, dissolving the emulsifier in the oil phase to obtain an oil phase mixed solvent, wherein the HLB value is 5. Wherein the oil phase is 85% of white oil, the emulsifier is 15% of Span80 and OP-10 by mass, and the mass ratio of Span80 to OP-10 is 4: 1.

And thirdly, slowly dripping the water-phase mixed solution prepared in the first step into the oil-phase mixed solvent prepared in the second step at the speed of 1 drop/second according to the mass ratio of 2:3, and fully stirring to obtain the emulsion. The total mass of the emulsion (approximatively, the total mass of the drag reducer) was taken as 100%, and the content of the emulsifier was calculated to be 9%.

And fourthly, introducing nitrogen into the emulsion to remove oxygen for 30min, adding an azo thermal dispersion initiator V044 (azobisisobutyrimidazoline hydrochloride (AIBI)) under the stirring conditions of 60 ℃ and 800r/min, and stirring at the temperature of 800r/min for reaction for 2 hours to obtain the emulsion drag reducer. Wherein the dosage of V044 is 0.03 percent based on the total mass of the drag reducer as 100 percent.

The number average molecular weight of the drag reducer obtained was 920 ten thousand as determined by gel permeation chromatography.

The evaluation of the drag reduction effect was conducted in the same manner as in example 1, and the results are shown in Table 1.

Example 5

In the monomer A, R₁Is methyl; in the monomer B, M is Na; in the monomer C, R₂And R₃Are each methyl, n₁Is 1; in the monomer D, R₄Is H, R₅Is butyl, n₂Is 2, R₆Is a cyclohexane group.

The process for preparing a drag reducing agent comprises the steps of:

firstly, dissolving each monomer in deionized water, and adjusting the pH value to 6.5 by using sodium hydroxide to obtain a water phase mixed solution. Wherein, the mass of the deionized water is taken as 100 percent, and the dosage of the monomer A, the monomer B, the monomer C and the monomer D is 20 percent, 6 percent, 4 percent and 0.5 percent in sequence.

And secondly, dissolving the emulsifier in the oil phase to obtain an oil phase mixed solvent, wherein the HLB value is 5. Wherein the oil phase is 85% of white oil, the emulsifier is Span40 and Tween40 with the total mass of 15%, and the mass ratio of Span40 to Tween40 is 1: 1.

And thirdly, slowly dripping the water-phase mixed solution prepared in the first step into the oil-phase mixed solvent prepared in the second step at the speed of 1 drop/second according to the mass ratio of 1:1, and fully stirring to obtain the emulsion. The total mass of the emulsion (approximatively, the total mass of the drag reducer) was taken as 100%, and the content of the emulsifier was calculated to be 7.5%.

And fourthly, introducing nitrogen into the emulsion to remove oxygen for 30min, adding sodium bisulfite at 40 ℃ under the stirring condition of 800r/min, adding ammonium persulfate after 30mins, and stirring and reacting for 3 hours at 800r/min at the temperature to obtain the milky drag reducer. Wherein the total mass of the drag reducer is 100 percent, the dosage of the sodium bisulfite is 0.01 percent, and the dosage of the ammonium persulfate is 0.01 percent.

The number average molecular weight of the drag reducer prepared was 880 ten thousand as determined by gel permeation chromatography.

The evaluation of the drag reduction effect was conducted in the same manner as in example 1, and the results are shown in Table 1.

Example 6

In the monomer A, R₁Is n-propyl; in the monomer B, M is K; in the monomer C, R₂Is isopropyl, R₃Is methyl, n₁Is 3; in the monomer D, R₄Is ethyl, R₅Is C₁₆Alkyl of n, n₂Is 5, R₆Is methyl cyclohexyl.

The process for preparing a drag reducing agent comprises the steps of:

firstly, dissolving each monomer in deionized water, and adjusting the pH value to 7 by using sodium hydroxide to obtain a water phase mixed solution. Wherein, the mass of the deionized water is taken as 100 percent, and the dosage of the monomer A, the monomer B, the monomer C and the monomer D is 20 percent, 6 percent, 4 percent and 0.5 percent in sequence.

And secondly, dissolving the emulsifier in the oil phase to obtain an oil phase mixed solvent, wherein the HLB value is 6. Wherein the oil phase is white oil accounting for 85 percent of the mass of the oil phase mixed solvent, and the emulsifier is Span60 and Tween80 accounting for 10 percent of the total mass, wherein the mass ratio of Span60 to Tween80 is 3: 1.

And thirdly, dropwise adding the water-phase mixed solution prepared in the first step into the oil-phase mixed solvent prepared in the second step at a mass ratio of 3:2 at a speed of 1 drop/second, and fully stirring to obtain an emulsion. The total mass of the emulsion (approximately equal to the total mass of the drag reducer) is taken as 100%, and the content of the emulsifier is calculated to be 4%.

And fourthly, introducing nitrogen into the emulsion to remove oxygen for 30min, adding Azobisisobutyronitrile (AIBN) under the stirring condition of 800r/min at 40 ℃, and stirring at 800r/min for reaction for 3 hours at the temperature to obtain the milky drag reducer. Wherein the dosage of the azodiisobutyronitrile is 0.05 percent based on the total mass of the drag reducer as 100 percent.

The number average molecular weight of the drag reducer prepared was 890 ten thousand as determined by gel permeation chromatography.

The evaluation of the drag reduction effect was conducted in the same manner as in example 1, and the results are shown in Table 1.

TABLE 1 examples	Drag reduction in fresh water	Drag reduction in highly mineralized brine
			Example 1	72.55％	70.03％
Example 2	74.71％	69.86％
			Example 3	73.77％	71.82％
Example 4	71.96％	70.88％
			Example 5	70.98％	71.75％
Example 6	72.76％	70.48％

As can be seen from table 1, the drag reducer of the present invention is able to resist high shear.

While the invention has been described with reference to specific embodiments, those skilled in the art will appreciate that various changes can be made without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, and method to the essential scope and spirit of the present invention. All such modifications are intended to be included within the scope of the present invention as defined in the appended claims.